Transporter for heavy objects at sea

ABSTRACT

A transporter for heavy objects at sea comprises an oblong structure with a U-shaped cross section and a prismatic enveloping surface, and comprises two long sides, an intermediate underside, an opposite open top side and two short sides. Ballasting chambers are arranged in each of the structure&#39;s eight corners which are formed by the points of intersection between the long sides, the underside, the open top side and the short sides, whereby the structure can be rotated by ballasting to a desired position in the water.

This application is the National phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/NO97/00344 which has an Internationalfiling date of Dec. 17, 1997

FIELD OF THE INVENTION

The invention concerns a transporter for heavy objects at sea,comprising an oblong structure with a U-shaped cross section and aprismatic enveloping surface, comprising two long sides, an intermediateunderside, an opposite open top side and two short sides.

DESCRIPTION OF THE BACKGROUND ART

Heavy objects, such as platform decks, platform jackets and bridgeelements are transported by sea on ships or barges. The object istransferred from and to the ship or the barge by hoisting cranes, theobject being pushed or pulled, or by means of rolling transport wherewheels or rollers are employed.

Another known method is to transfer objects by ballasting the ship orthe barge and moving it into a passage under the object, whereupon theship or the barge is deballasted, thus causing it to be raised andleaving the object lying on the ship or the barge. The object may beunloaded in a similar manner by deballasting the ship or the barge, thuscausing it to be lowered, with the object supported by lower-lyingsupports on the side of the ship or the barge.

These known methods of transporting heavy objects at sea work well aslong as the object does not require to be turned, and as long as thelevel differences which have to be obtained by theballasting/deballasting are relatively small. When using a ship or abarge, however, it is not possible to turn an object, such as a mast ora platform jacket, which is so large that it has to be transportedhorizontally, but which has to be turned into a vertical position beforebeing installed in position.

U.S. Pat. No. 5,111,764 describes a method for recovering thesubstructure of an offshore platform. A floating barge is usedcomprising a ballastable hull having a deck suitable for receiving thesubstructure in a substantially horizontal position and includingballastable floats disposed above the deck to right and to left of theintended location for the substructure. The hull and the floats areballasted so that although it does not sink, the barge moves down intothe water and tilts into a position where its deck can be moved againstone of the faces of the substructure. The barge is fixed to thesubstructure, the substructure is disconnected from the sea bed, ballastis removed from the barge to return it to a position where it isfloating and carrying the substructure, and the barge is moved to thedesired location for unloading the substructure. The invention isapplicable to recovering substructures of large dimensions. With themethod and barge according to U.S. Pat. No. 5,111,764 it is therebypossible to a certain extent to transport heavy objects at sea, and toturn the object in the water. The degree of attachment and rotationalmovement which are achieved, however, are limited to the attachment androtation.

SUMMARY OF THE INVENTION

The object of the invention is to provide a transporter which comparedwith known devices for transport of heavy objects at sea has greaterpossibilities for securing the object, and which also has greaterpossibilities for turning the object in the water.

The object is further to provide a transporter which will also be ableto be used for installation or removal of a deck on and from a platformjacket respectively, and installation or removal of a platform jacket onand from the seabed respectively.

The latter object is achieved with a transporter of the type mentionedin the introduction, which, is also characterized by the features whichare stated in the claims in the applicant's copending Norwegian patentapplications Nos. 973561 and 973562.

The invention therefore includes in a transporter for heavy objects atsea, comprising an oblong structure with a U-shaped cross section and aprismatic enveloping surface, comprising two long sides, an intermediateunderside, an opposite open top side and two short sides. In theinvention ballasting chambers are arranged in each of the structure's 8corners which are formed by the points of intersection between the longsides, the undersides, the open top side and the short sides, wherebythe structure can be rotated by means of ballasting into a desiredposition in the water. Moreover, the transporter is provided withattachment means for securing objects which have to be transported.

The ballasting and deballasting are performed in the known manner bypumping water in and out of the ballasting chambers by means of pumps,piping and valves. When the structure is rotated, those ballastingchambers which have to be moved downwards during rotation and afterrotation will be located at the bottom are ballasted, while at the sametime those ballasting chambers which have to be moved upwards duringrotation and after rotation will be located at the top are deballasted.A computer calculates which ballasting chambers have to be ballasted anddeballasted in order to achieve the desired rotation and final positionof the transporter in the water, while simultaneously calculating themetacentric height and monitoring the progress of theballasting/deballasting and the rotation. The computer communicates withan operator, who in turn gives orders concerning the execution of thenecessary ballasting and deballasting. In this context the informationon the metacentric height is very important, since a stable rotation ofthe transporter, without sudden movements, is dependent on themaintenance of a constant positive metacentric height.

The actual movement of the transporter will be conducted by tugs.

The transporter's ballasting chambers are preferably provided inlongitudinal pontoons in the corner areas between the transporter'sunderside and long sides, and at the top of the long sides. The resultis a structure which offers little resistance to movement in the water,and which is consequently suited for transport.

In a preferred embodiment the transporter has attachment means forsecuring objects, for example in the form of brackets or beams attachedto the pontoons.

The above and further preferred embodiments of the invention will beseen in the detailed description.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail in association with adescription of specific embodiments, and with reference to the drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and, in which:

FIG. 1 is a perspective view of a transporter according to theinvention,

FIG. 2 illustrates the transporter in FIG. 1 viewed from a short side,

FIG. 3 is a perspective view of a second transporter according to theinvention,

FIG. 4 illustrates a transporter according to the invention, viewed fromthe side,

FIG. 5 illustrates a tansporter according to the invention in use duringa lifting/transport operation at sea, and

FIGS. 6a-h illustrate a sequence in which the transporter in FIG. 4 isused to install a bridge element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 elucidate the core of the invention. FIG. 1 illustrates atransporter according to the invention in perspective, and FIG. 2illustrates the transporter viewed from a short side, in the directionshown by the arrow P in FIG. 1. The transporter in FIGS. 1 and 2consists of two long sides 2 and an intermediate underside 3, whichtogether form an oblong structure with a U-shaped cross section. Thethree sides which form the U-shaped cross section together with an opentop side 4, which is located opposite the underside 3, and two shortsides 23, form a body with a prismatic enveloping surface.

Thus in the illustrated embodiments, the top side 4 and the short sides23 are only imaginary surfaces or sides. Nor are the long sides 2 andthe underside 3 real surfaces, and should be understood as planes whichcontain structural elements which constitute the transporter accordingto the invention.

The ballasting chambers 5 are provided in pontoons 6 in each of thetransporter's 8 corners, i.e. the 8 corners which are formed by thepoints of intersection between the surfaces or the sides which form theprismatic enveloping surface. More correct, each of these 8 corners isdefined by the intersection between three edgelines which in turn areintersecting lines between adjacent planes or sides in the prismaticbody. A structure is thereby formed in which the ballasting chambers 5are arranged in all the extremities, thereby permitting ballast orbuoyancy to be brought to all these extremities.

The transporter in FIGS. 1 and 2 further consists of transverseconnecting elements 7 and longitudinal connecting elements 13 which bindthe pontoons 6 together. In addition, not shown, the transportercomprises piping, valves, pumps with motors and control equipment forperforming the ballasting/deballasting. The ballasting/deballasting isremotely controlled by means of not shown communication equipment.Alternatively, the ballasting/deballasting may be performed with anumbilical which contains both pressurised water for ballasting andpressurised air for deballasting, together with pressurised fluid foroperation and control of the valves.

By ballasting or deballasting the various ballasting chambers 5 it ispossible to rotate the transporter in FIGS. 1 and 2 into any desiredposition in the water. Calculations and tests confirm this property ofthe transporter.

FIG. 3 illustrates a transporter which like the transporter in FIGS. 1and 2 consists of two long sides 2 and an intermediate underside 3 whichtogether form an oblong structure with a U-shaped cross section. Lowerlongitudinal pontoons 9 are arranged in the longitudinal corner areasbetween the underside 3 and the long sides 2, and upper longitudinalpontoons 8 are arranged in the upper section of the long sides 2,between the long sides and the imaginary top side. At each end of thelongitudinal pontoons 8 and 9 there are arranged ballasting chambers,which are located in one of the corners in the imaginary prismaticenveloping surface around the transporter. In the same way as in FIGS. 1and 2 the transporter in FIG. 3 forms a structure in which each of theextremities can be ballasted or deballasted, thus making it possible forthe structure to be rotated into any desired position in the water.

In the embodiment in FIG. 3 the longitudinal pontoons 8, 9 extend in theentire transporter's longitudinal direction. The ballasting chambers inthe transporter's corners may extend from the end of the longitudinalpontoons all the way into the area in the middle of the pontoon, buteach pontoon is preferably divided into several chambers. This divisioninto several chambers is performed both in order to achieve a simplercontrol of the ballasting/deballasting, and to increase the structure'sstability in the event of a functional fault or damage to the structurewhich results in an uncontrolled ballasting or deballasting.

The longitudinal pontoons are preferably composed of tubes or have atubular cross section, since this is advantageous both with regard tomanufacture, internal volume and resistance to internal and externalpressure.

Like the transporter illustrated in FIGS. 1 and 2 the transporterillustrated in FIG. 3 has transverse connecting elements 7 provided inthe long sides 2 and the underside 3, in order to bind the longitudinalpontoons together. These transverse connecting elements are preferablyalso composed of ballastable pontoons or tubes, thus enabling them tocontribute to the ballasting/deballasting of the transporter.

During transport of the transporter, which is conducted by tugs, it isadvantageous to deballast the transporter, so that it offers leastpossible resistance to motion. In most cases this means that it isadvantageous to place the transporter in a position where it is lyingwith the underside 3 down, as high as possible in the water.

In order to increase the capacity during ballasting/deballasting, and toprovide an area for placing objects which are to be transported, thetransporter in FIG. 3 comprises two longitudinal pontoons 24 arranged inthe transporter's underside 3. In a preferred embodiment, as shown inFIG. 3, these two longitudinal pontoons together with their respectivetransverse connecting elements 7 are, compared to the surface formingthe underside 3, located closer to the transporter's central area. Thisplacing of the longitudinal pontoons 24 and the respective transverseconnecting elements 7 has the effect that they are at least partlylocated above the water when the transporter is lying deballasted in thewater with the underside down, with the result that during transportthey offer little or no resistance to the movement in the water.

The object which are to be transported can be placed in differentlocations on the transporter, especially on the underside 3 or the upperlongitudinal pontoons 8. In order to obtain easy access for insertingobjects which have to be transported to the area above the underside 3,the transporter's short sides are open. This is most clearly illustratedin FIG. 2, where the short side is indicated by reference numeral 23.

In order to secure objects which are to be transported the transporterillustrated in FIG. 3 has attachment means in the form of beams 10 onthe longitudinal pontoons in the transporter's underside, beams 20 onthe upper longitudinal pontoons, and beams 21 on the lower longitudinalpontoons. The beams 10, 20, 21 may be provided with boltholes forattaching the object by bolting, eyes or lugs for attaching the objectsby wives, or other appropriate attachment means.

In order to increase the transporter's usefulness, in the embodimentillustrated in FIG. 3 it has at one end a recess 11, formed due to thefact that the undersides 3 in the longitudinal direction have a shorterextension than the long sides 2. When the transporter is lying in thewater with the underside 3 down, the long sides 2 can thereby be movedon the outside of a support for an object which has to be transferred tothe transporter. This will be discussed below in more detail withreference to FIG. 5.

Furthermore, in the transporter illustrated in FIG. 3 the lowerlongitudinal pontoons 9 are longer than the upper longitudinal pontoons8 at the end in which the recess is located, with the result that thelower longitudinal pontoons have portions or sections 12 which in thelongitudinal direction project past the underside 3 and the long sides2. The lower longitudinal pontoons' outwardly projecting sections 12contribute to keeping the transporter horizontal when it is lying in thewater with the underside down, a ballasting or deballasting or theseoutwardly projecting sections providing a moment which can counteractthe effect of the weight of an object which is placed on the underside 3or the upper longitudinal pontoons 8.

FIG. 4 illustrates a transporter according to the invention viewed fromthe side, located in the water 18. This illustrates how an object 14 canbe placed on the upper longitudinal pontoons 8 in an area which in thetransporter's longitudinal direction is located opposite the outwardlyprojecting sections 12 of the lower longitudinal pontoons 9. Thisplacing of the object 14 will attempt to turn the transporter, thusraising the end where the outwardly projecting sections 12 are located.In order to counteract this the outwardly projecting sections 12 can beballasted. Similarly, a placing of an object 15 at the end of thetransporter where the outwardly projecting sections 12 are located willattempt to turn this end down into the water 18, which can becounteracted by a deballasting of the outwardly projecting sections 12.

FIG. 5 illustrates a transporter according to the invention in useduring a lifting/transport operation at sea. Here the transporter islying with the lower pontoons 9 under the water 18, and the long sideshave been moved on to the outside of a platform jacket 17 which isstanding on the seabed 19. The platform jacket is located in the recess11 in the underside 3, which is not shown, since the underside islocated down in the water. Attachment means in the form of supportingsections on the transporter's long side have been brought into abutmentagainst a platform deck 16 which rests on the jacket 17. When thetransporter is deballasted it will be raised in the water, therebyenabling the deck 16 to be lifted from the jacket 17, and taken away bymeans of the transporter.

FIGS. 6a-h illustrate a sequence in which the transporter in FIG. 4 isused to transport and install a bridge element. In FIG. 6a a transporter1 is lying horizontally in the water 18, beside a bridge element 30. Thebridge element 30 is resting on two supports 31, a front support and arear support indicated by dotted lines. It should be understood that therear support is located behind the front support, and that the bridgeelement 30 in the direction perpendicular to the transporter'slongitudinal direction has an extension which is larger than thetransporter's width. Further, between the supports 31 there is a recesswhich is sufficiently wide and deep to contain the transporter 1.

FIG. 6b illustrates the transporter in a position where it is soballasted that it has sunk down in the water under the bridge element30, and is partially rotated into a position where it can lift thebridge element.

FIG. 6c illustrates the transporter in a vertical position, where it haslifted the bridge element off the supports, so that the bridge elementis resting on the outwardly projecting sections 12 of the lower pontoons9 and a cross element 7.

FIGS. 6d and 6 e illustrate the transporter with the bridge elementduring and after rotation to a horizontal position in the waterrespectively, for transport to a destination.

FIG. 6f illustrates the transporter during rotation to a verticalposition after arrival at the destination, and

FIG. 6g shows the transporter in a vertical position, raised to thecorrect height for transfer of the bridge element.

FIG. 6h illustrates the bridge element transferred from the transporter,as it should be understood that the bridge element is attached to notshown adjacent bridge elements or bridge foundations. After the transferthe transporter is lowered into the water and removed.

Compared to the introductory known device, represented by Norwegianpatent application No. 91 0358, the transporter according to theinvention therefore provides greater possibilities for securing theobject, and greater possibilities for turning the object in the water.Thus the transporter according to the invention fulfils the object ofthe invention.

Further advantageous embodiments and applications of the transporter,associated with removal of a platform deck from a jacket, and removal ofa jacket from the seabed, are illustrated and described in theapplicant's copending Norwegian patent applications Nos. 973561 and973562. The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A transporter for heavy objects at sea,comprising: an oblong structure with a U-shaped cross section and aprismatic enveloping surface having eight corners, the oblong structurehaving two long sides, an intermediate underside, an opposite open topside and two short sides; ballasting chambers being provided in each ofthe eight corners of the prismatic enveloping surface, whereby thestructure can be rotated by ballasting to a desired position in water;and attachment means for securing objects which are to be transported tothe transporter.
 2. The transporter according to claim 1, wherein theballasting chambers in the corners of the prismatic enveloping surfaceare provided in ballastable pontoons arranged in four longitudinalcorner areas between the long sides, the underside and the open top sideof the structure, the structure further comprising transverse connectingelements provided in the long sides and underside for connecting thepontoons together.
 3. The transporter according to claim 2, wherein thepontoons in the longitudinal corner areas include longitudinal pontoons.4. The transporter according to claim 3, wherein the longitudinalpontoons in the longitudinal corner areas extend along an entirelongitudinal direction of the transporter and have a ballasting chamberat each end, which ballasting chambers in the longitudinal direction areextendable towards the middle of the pontoon.
 5. The transporteraccording to claim 1, wherein the underside has at least onelongitudinal pontoon.
 6. The transporter according to claim 5, whereinat least one of the longitudinal pontoons, compared to a surface formingthe underside, is located closer to a central area of the transportersuch that when the transporter is lying in the water with the undersidedown, the at least one longitudinal pontoon in the underside is locatedat least partly above the water.
 7. The transporter according to claim1, wherein the transporter is open in at least one of the short sides tothereby provide easy access for objects which are to be placed in anarea above the underside.
 8. The transporter according to claim 1,wherein one end of the underside has a recess formed due to theunderside in the longitudinal direction of the transporter has a shorterextension than the long sides, whereby when the transporter is lying inthe water with the underside down, the long dies can be moved on to theoutside of a support for an object which is to be transferred to thetransporter.
 9. The transporter according to claim 8, wherein thepontoons in the longitudinal corner areas include longitudinal pontoonsand wherein the longitudinal pontoons between the underside and the longsides at an end of the transporter adjacent the recess have projectingsections which project past the long sides in the longitudinal directionwhereby when at least a portion of the pontoons are deballasted, theprojecting sections contribute to keeping the transporter horizontalwhen lying in the water with the underside down and further support anobject at the same end of the transporter.
 10. The transporter accordingto claim 3, wherein the longitudinal pontoons between the underside andthe long sides have projecting sections which project past the longsides in the longitudinal direction whereby when at least a portion ofthe pontoons are deballasted, the projecting sections contribute tokeeping the transporter horizontal when lying in the water with theunderside down and further support an object at the same end of thetransporter.
 11. The transporter according to claim 3, wherein thelongitudinal pontoons are composed of tubes.
 12. The transporteraccording to claim 2, wherein the transverse connecting elements in thelong sides and underside of the transporter are composed of at least oneof pontoons and tubes.
 13. The transporter according to claim 12,wherein the at least one of pontoons and tubes are ballastable.
 14. Thetransporter according to claim 1, wherein the oblong structure is madefrom hollow tubes.
 15. A method for at least transporting heavy objectsat sea, the method comprising the steps of: providing an oblongstructure with a U-shaped cross section and a prismatic envelopingsurface having eight corners, the oblong structure having two longsides, an intermediate underside, an opposite open top side and twoshort sides; rotating the structure to any desired position in the waterby ballasting and deballasting selected ballasting chambers, each of theeight corners of the prismatic enveloping surface having at least one ofthe ballasting chambers; and attaching at least one object to betransported to the transporter after the step of rotating.
 16. Themethod for transporting heaving objects at sea according to claim 15,further comprising the steps of: bringing the transporter into abutmentwith a jacket supporting the at least one object to be transported; andlifting the at least one object from the jacket during the step ofrotating to thereby detach the at least one object from the jacket. 17.The method for transporting heaving objects at sea according to claim15, wherein the at least one object is a platform deck and wherein themethod further comprises the step of moving the platform through the seaon the transporter.
 18. A portion of a disassembled offshore platformincluding at least one of the jacket and platform produced in accordancewith the steps of claim
 17. 19. A portion of a disassembled offshoreplatform including a jacket produced in accordance with the steps ofclaim
 16. 20. A portion of a disassembled offshore platform including atleast one object produced in accordance with the steps of claim 15.